In recent years, nano-materials and nanotechnology have become the key point for research in every nation. A nanomaterial usually refers to a material with a size range from 1 nm to 100 nm. Since nanoparticles have a very small particle size and the number of atoms constituting the nanoparticle is far less than the typical particle, it thus has a great surface area and a high surface atomic ratio, and thereby the nanoparticle itself has a quantum effect. Therefore, nanoparticles have many specific properties and potential applications in the aspects of the catalyst, the electrode, the optical property and the mechanical property. Hence, nanomaterials and nanotechnology can be applied to various fields that have developmental potential.
Among the many metal materials for producing nanoparticles, gold was the earliest one to be investigated generally. Gold nanoparticles are considered as the best material for use in the living body due to its many advantages such as simple preparation method and high biocompatibility, such that biomedical research and development of gold nanoparticles has increased year by year.
The near infrared ray (NIR), especially between the region 1000˜1350 nm, is known as the biological window in which the electromagnetic wave has better tissue penetration while not being absorbed by the skin tissue to achieve the detection and treatment for the deep tissues. Meanwhile, the biological tissue significantly reduces generation of autofluorescence when irradiated by the NIR. It goes without saying that a material that has the abilities of absorbing the NIR and generating the fluorescence can be applied in the biomedical field. However, an NIR-absorber with a size less than 100 nm is not available in that region, and so the application of the NIR-absorber in the living body is limited.
In view of the drawbacks of the prior art, the present invention describes a nanostructure which has a dominant component of gold having the ability of absorbing the NIR, and has the functions of combining the targeted drug, imaging and treatment. This nanostructure can serve as an imaging agent to combine with existing ultrasound and endoscope technology currently in development to become a novel diagnostic and treatment platform and to provide more applications. The summary of the present invention is below.